[jluerken]

Ok its working for me now.

It seems that it had something to do with the <div> Tags.

Here my solution:

At the end of the postbit template at:

<!-- ADs after first forum post -->
<if condition="!is_member_of($bbuserinfo, 5,7) AND !$GLOBALS['FIRSTPOSTID']">  
<if condition="$show['spacer']">
	<div>
	$spacer_open
</if>
  <table class="tborder" id="post$post[postid]" cellpadding="$stylevar[cellpadding]" cellspacing="$stylevar[cellspacing]" border="0" width="100%" align="center">
    <tr> 
<td class="alt2" width="17%" nowrap>
$vbphrase[google_ads_hint]
</td>
<td class="alt2" width="83%">
<center>

YOUR AD HERE

</center>
</td></tr></table>

<if condition="$show['spacer']">
	</div>
	$spacer_close
</if>
</if>

Create a global phrase called "google_ads_hint" to get some text beside your ads like on my screenshot.
Remove the whole TD tag if you don't want this.